Stressed plant, ultrasound screams?

According to an experiment conducted by a research team at Tel Aviv University in Israel, plants were also found to scream ultrasonically when exposed to stress.

Plants are easy to think of as beings that do not move still no matter what happens around them, but not only humans and animals but also plants respond to external stimuli in various ways. In a 2014 experiment with mimosa, it was found that mimosa has a kind of learning function, and research results show that plants can hear the sound of chewing when eaten by pests.

According to a study published in 2019, it has been found that among sweet potato varieties, they use odor to transmit red moisture to surrounding individuals. Plants never respond to external stimuli, but rather than humans can imagine.

In a 2013 study conducted by Tel Aviv University, a plant was equipped with a recording device to detect very small sounds generated by plant stems. This sound is caused by bubbles formed in plants that are stressed by drought, causing vibrations in tissues that carry water.

In past studies, sound was detected with a recording device attached to the plant itself, but the research team conducted a new experiment to investigate whether the sound made by plants can be heard in the air. Tomatoes and tobacco, which are widely cultivated worldwide crops, were placed in pairs in greenhouses and soundproof rooms, and microphones were installed at a distance of 10 cm. The crops were placed under three conditions: one subject to water shortage stress due to drought state, one subject to physical damage stress by putting a sheath on the stem, and one without stress. Through this, it was checked whether the sound of sweat was recorded in the microphone through the air.

As a result of the experiment, all the crops subjected to stress emit ultrasonic waves that are inaudible to human ears at 10-100 kHz, and sound was recorded through a microphone 10 cm away from both the greenhouse and the soundproof room. This sound is inaudible to human ears, but according to the research team, some animal species can detect the sound produced by plants from several meters away.

Also, in this experiment, it was confirmed that the frequency of making sounds differs depending on the type of plant and the type of stress. For example, a tomato placed in a drought condition makes an average of 35 times per hour, and a tomato that is injured makes about 25 noises per hour. On the other hand, cigarette beeps in drought condition are 11 times per hour, and those injured are 15 times per hour. Even with the same stress factor, different types of plants produce different results. In addition, the general crops used as the control group produced only a frequency less than once per hour.

The research team also investigated whether the plant type and stress can be determined only by the sound of the plant ringing, focusing on the fact that the sound of each crop has different frequencies depending on the stress factor. It was attempted to classify the sound by learning a machine learning algorithm, and it is said that it was possible to judge three situations, such as drought and injured, with sound only.

The research team predicts that using this technology, it will be possible to select drought-resistant individuals from equipment installed by farms in their fields. The study identified conditions such as exposure to disease, too high soil salinity, and inadequate temperature, so it is not known whether the plant responds to any stress and makes a sound. However, in addition to tomatoes and tobacco, it has succeeded in recording similar sounds in various plants. In addition, because the sound made by plants can be detected by other animals, insects such as moths have the potential to select plants to lay eggs by listening to the sounds made by plants, the research team suggested. However, some point out that this is too leap because it has not confirmed the actual insect reaction. Related information can be found here .